The game is the best in AC series so far and surely a miss if u've haven't owned a copy. I'm still exploring Rome in the medieval times...half of the time goes for it. The Story mode campaign starts off exactly from where AC2 ends. Though great, however it does matter the least to me as major time is spent playing on the multiplayer missions as an abstergo agent. In the story mode I enjoy Romulus-LAIR missions due to the time-challenge for Full Synchronization and Leornado's assignments(not revealing-due to spoilers). There's so much in this game to complete apart from story-mode. You definitely mite be needing a walkthru to complete all the secret locations, and for collecting all flags and feathers
And now with Assassin's Creed 3 down the line, I have a reason to hurry up ending the story mode.